Method for producing organic light-emitting element, organic display panel, organic light-emitting device, method for forming functional layer, ink, substrate, organic light-emitting element, organic display device, and inkjet device

ABSTRACT

To provide a method of efficiently manufacturing an organic light-emitting element with excellent light-emitting characteristics by application, the method includes: preparing ink and filling an inkjet device having an ink ejection nozzle with the ink; preparing a substrate having a base layer including a first electrode; and positioning the inkjet device above the substrate, and causing the inkjet device to eject a drop of the ink onto the base layer, wherein, in the preparation of the ink, a value Z denoting a reciprocal of the Ohnesorge number Oh determined by density ρ (g/m 3 ), surface tension γ (mN·m), and viscosity η (mPa·s) of the ink and a diameter r (mm) of the ink ejection nozzle satisfies Formula 1, in the ejection of the drop of the ink, speed V (m/s) of the ejected drop satisfies Formula 2, and the value Z and the speed V (m/s) satisfy Formula 3.

TECHNICAL FIELD

The present invention relates to a method of manufacturing an organiclight-emitting element, an organic display panel, an organiclight-emitting device, a method of forming a functional layer, ink, asubstrate, an organic light-emitting element, an organic display device,and an inkjet device.

BACKGROUND ART

Organic light-emitting elements, which have recently been studied anddeveloped, are light-emitting elements making use of the phenomenon ofelectroluminescence occurring in functional material and have astructure in which an organic light-emitting layer formed fromfunctional material is interposed between an anode and a cathode. In aprocess of manufacturing such organic light-emitting elements,functional material is deposited on a substrate by a vapor depositionmethod using a mask to form a functional layer including an organiclight-emitting layer.

As an alternative to the vapor deposition method, an application methodhas been proposed (Patent Literature 1). In the application method, thefunctional material is dissolved in a solvent to form ink, the ink isapplied to a substrate by ejecting the ink from an ink ejection nozzleof an inkjet device, and then the solvent is volatilized to form anorganic light-emitting layer. In this method, there is no need toperform the process in a vacuum chamber and to use the mask. This methodis thus preferred in terms of mass production.

CITATION LIST Patent Literature

[Patent Literature 1]

-   Japanese Patent Application Publication No. 2009-267299

SUMMARY OF INVENTION Technical Problem

In order to manufacture an organic light-emitting element with excellentlight-emitting characteristics by the application method, it isnecessary to form an organic light-emitting layer having a uniform filmthickness and shape by applying ink exactly to a light-emittinglayer-forming region on the substrate. To this end, ink drops ejectedfrom the inkjet device have to have preferred flight characteristics.That is to say, the ink drops have to arrive straight at a desireddestination without breaking up.

The flight characteristics of ink drops, however, are variable dependingon the properties of ink, such as the density, the surface tension, theviscosity, and a droplet diameter of the ink. It is not easy to controlthe flight characteristics, because correlations among these propertiesare unclear. The flight characteristics also vary depending on factorsother than the properties of the ink, such as the droplet diameter ofthe ink, which is determined primarily by a diameter of the ink ejectionnozzle, and speed at which ink drops are ejected from the ink ejectionnozzle. This makes it more difficult to control the flightcharacteristics.

It is a fact that, each time ink or an inkjet head is replaced with anew one, the flight characteristics are evaluated by actually ejectingthe ink by using the new ink or inkjet head while making modificationsto various factors affecting the flight characteristics, to seek acondition providing preferred flight characteristics. It takes a longtime to determine the condition. To address the above-mentioned problem,it is necessary to develop technology to estimate the conditionproviding preferred flight characteristics with ease and accuracy.

In view of the above-mentioned problem, the primary objective of thepresent invention is to provide a method of efficiently manufacturing anorganic light-emitting element with excellent light-emittingcharacteristics by an application method, through easy and accurateestimation of the condition providing preferred flight characteristics.

Solution to Problem

To achieve the above-mentioned objective, a method of manufacturing anorganic light-emitting element pertaining to one aspect of the presentinvention includes: preparing ink including functional material as amaterial for a functional layer and a solvent dissolving the functionalmaterial, and filling an inkjet device having an ink ejection nozzlewith the ink, the functional material having a weight-average molecularweight greater than zero and equal to or less than 100,000; preparing asubstrate having a base layer including a first electrode; positioningthe inkjet device above the substrate, and causing the inkjet device toeject a drop of the ink onto the base layer of the substrate; formingthe functional layer by drying the ink ejected onto the base layer ofthe substrate; and forming a second electrode above the functionallayer, wherein, in the preparation of the ink, when a value Z denotes areciprocal of the Ohnesorge number Oh determined by density ρ (g/m³),surface tension γ (mN·m), and viscosity η (mPa·s) of the ink and adiameter r (mm) of the ink ejection nozzle, the value Z is within arange of Formula 1, in the ejection of the drop of the ink, speed V(m/s) of the ejected drop of the ink is within a range of Formula 2, andthe value Z and the speed V (m/s) satisfy Formula 3.0.7≦Z≦13where Z=1/Ohnesorge number Oh=(r·ρ·γ)^(1/2)/η  (Formula 1);3≦V≦6  (Formula 2); andV≦−2.17 Ln(Z)+8.47  (Formula 3).

Advantageous Effects of Invention

In the method of manufacturing the organic light-emitting elementpertaining to one aspect of the present invention, when the value Zdenotes the reciprocal of the Ohnesorge number Oh determined by thedensity ρ (g/m³), the surface tension γ (mN·m), and the viscosity η(mPa·s) of the ink and the diameter r (mm) of the ink ejection nozzle,the value Z is within the range of Formula 1 shown above, the speed V(m/s) of the ejected drop of the ink is within the range of Formula 2shown above, and the value Z and the speed V (m/s) satisfy Formula 3shown above. Since only two variables, i.e. the value Z and the speed V(m/s), are used, it is easy to estimate a variation of the flightcharacteristics. Furthermore, since there are high correlations betweenthe value Z and the flight characteristics and between the speed V (m/s)and the flight characteristics, accurate estimation is possible.Therefore, the condition providing preferred flight characteristics canbe estimated with ease and accuracy. As a result, the organiclight-emitting element with excellent light-emitting characteristics canefficiently be manufactured by the application method.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates three forces affecting flight characteristics of anink drop.

FIG. 2 illustrates ink drop placement accuracy.

FIG. 3 shows experimental results on a relation between a value Z andthe placement accuracy.

FIG. 4 shows the relation between the value Z and the placementaccuracy.

FIG. 5 shows a relation between ejection speed V and the placementaccuracy.

FIG. 6 shows a relation between the ejection speed V and a variation ofthe ejection speed.

FIGS. 7A, 7B, 7C, and 7D illustrate examples of how an ink drop breaksup.

FIG. 8 shows a relation between the value Z and a satellite generationspeed.

FIGS. 9A and 9B illustrate examples of an ink drop in an area I of FIG.8.

FIGS. 10A and 10B illustrate examples of an ink drop in an area II ofFIG. 8.

FIGS. 11A and 11B illustrate examples of an ink drop in an area III ofFIG. 8.

FIG. 12 shows experimental results on the relation between the value Zand the satellite generation speed.

FIG. 13 shows the relation between the value Z and the satellitegeneration speed.

FIG. 14 shows relations between the value Z and the satellite generationspeed, and between the value Z and the placement accuracy.

FIG. 15 shows a relation among the value Z, concentration of ink, andviscosity η of the ink.

FIG. 16 is a schematic diagram illustrating a laminated structure oflayers included in an organic display panel pertaining to one aspect ofthe present invention.

FIG. 17 illustrates a structure of an inkjet device pertaining to oneaspect of the present invention.

FIGS. 18A to 18G are a process chart showing a method of manufacturingan organic light-emitting element pertaining to one aspect of thepresent invention.

FIGS. 19A to 19E are a process chart showing the method of manufacturingthe organic light-emitting element pertaining to one aspect of thepresent invention.

FIG. 20 is a perspective view illustrating an organic display devicepertaining to one aspect of the present invention and the like.

FIG. 21 illustrates an overall structure of a display device pertainingto one aspect of the present invention.

FIGS. 22A and 22B illustrate an organic light-emitting device pertainingto one aspect of the present invention.

DESCRIPTION OF EMBODIMENTS

The following describes a method of manufacturing an organiclight-emitting element, an organic display panel, an organiclight-emitting device, a method of forming a functional layer, ink, asubstrate, an organic light-emitting element, an organic display device,and an inkjet device pertaining to one aspect of the present invention,with reference to the drawings.

[Overview of One Aspect of Present Invention]

A method of manufacturing an organic light-emitting element pertainingto one aspect of the present invention includes: preparing ink includingfunctional material as a material for a functional layer and a solventdissolving the functional material, and filling an inkjet device havingan ink ejection nozzle with the ink, the functional material having aweight-average molecular weight greater than zero and equal to or lessthan 100,000; preparing a substrate having a base layer including afirst electrode; positioning the inkjet device above the substrate, andcausing the inkjet device to eject a drop of the ink onto the base layerof the substrate; forming the functional layer by drying the ink ejectedonto the base layer of the substrate; and forming a second electrodeabove the functional layer, wherein, in the preparation of the ink, whena value Z denotes a reciprocal of the Ohnesorge number Oh determined bydensity ρ (g/m³), surface tension γ (mN·m), and viscosity η (mPa·s) ofthe ink and a diameter r (mm) of the ink ejection nozzle, the value Z iswithin a range of the above-mentioned Formula 1, in the ejection of thedrop of the ink, speed V (m/s) of the ejected drop of the ink is withina range of the above-mentioned Formula 2, and the value Z and the speedV (m/s) satisfy the above-mentioned Formula 3.

In a particular aspect of the method of manufacturing the organiclight-emitting element pertaining to one aspect of the presentinvention, the value Z is two or more and is ten or less, and the speedV is 3 m/s or more and is 5 m/s or less.

In a particular aspect of the method of manufacturing the organiclight-emitting element pertaining to one aspect of the presentinvention, the density ρ of the ink is more than 827 g/m³ and is 1190g/m³ or less, the surface tension γ of the ink is more than 27.3 mN·mand is 41.9 mN·m or less, the viscosity η of the ink is more than 2.4mPa·s and is 35.0 mPa·s or less, and the diameter r of the ink ejectionnozzle is 0.02 mm or more and is 0.03 mm or less.

In a particular aspect of the method of manufacturing the organiclight-emitting element pertaining to one aspect of the presentinvention, in the preparation of the substrate, the substrate has aplurality of openings corresponding to respective pixel units andincludes a plurality of banks each formed above the base layer topartition adjacent pixel units, and, in the ejection of the drop of theink, drops of the ink are ejected onto the base layer in regionscorresponding to the openings between the banks.

An organic display panel pertaining to one aspect of the presentinvention utilizes the organic light-emitting element manufactured bythe above-mentioned method.

An organic light-emitting device pertaining to one aspect of the presentinvention utilizes the organic light-emitting element manufactured bythe above-mentioned method.

An organic display device pertaining to one aspect of the presentinvention utilizes the organic light-emitting element manufactured bythe above-mentioned method.

A method of forming a functional layer pertaining to one aspect of thepresent invention includes: preparing ink including functional materialas a material for the functional layer and a solvent dissolving thefunctional material, and filling an inkjet device having an ink ejectionnozzle with the ink, the functional material having a weight-averagemolecular weight greater than zero and equal to or less than 100,000;preparing a substrate on which the functional layer is to be formed;positioning the inkjet device above the substrate, and causing theinkjet device to eject a drop of the ink onto the substrate; and formingthe functional layer by drying the ink ejected onto the substrate; and,wherein, in the preparation of the ink, when a value Z denotes areciprocal of the Ohnesorge number Oh determined by density ρ (g/m³),surface tension γ (mN·m), and viscosity η (mPa·s) of the ink and adiameter r (mm) of the ink ejection nozzle, the value Z is within arange of the above-mentioned Formula 1, in the ejection of the drop ofthe ink, speed V (m/s) of the ejected drop of the ink is within a rangeof the above-mentioned Formula 2, and the value Z and the speed V (m/s)satisfy the above-mentioned Formula 3.

In a particular aspect of the method of forming the functional layerpertaining to one aspect of the present invention, the value Z is two ormore and is ten or less, and the speed V is 3 m/s or more and is 5 m/sor less.

In a particular aspect of the method of forming the functional layerpertaining to one aspect of the present invention, the density ρ of theink is more than 827 g/m³ and is 1190 g/m³ or less, the surface tensionγ of the ink is more than 27.3 mN·m and is 41.9 mN·m or less, theviscosity η of the ink is more than 2.4 mPa·s and is 35.0 mPa·s or less,and the diameter r of the ink ejection nozzle is 0.02 mm or more and is0.03 mm or less.

An ink pertaining to one aspect of the present invention is ejected ontoa substrate by an inkjet device having an ink ejection nozzle, is driedto form a functional layer, and includes: functional material as amaterial for the functional layer, the functional material having aweight-average molecular weight greater than zero and equal to or lessthan 100,000; and a solvent dissolving the functional material, wherein,when a value Z denotes a reciprocal of the Ohnesorge number Ohdetermined by density ρ (g/m³), surface tension γ (mN·m), and viscosityη (mPa·s) of the ink and a diameter r (mm) of the ink ejection nozzle,the value Z is within a range of the above-mentioned Formula 1, speed V(m/s) at which the ink is ejected is within a range of theabove-mentioned Formula 2, and the value Z and the speed V (m/s) satisfythe above-mentioned Formula 3.

In a particular aspect of the ink pertaining to one aspect of thepresent invention, the ink includes the solvent and the functionalmaterial as a material for the functional layer of an organiclight-emitting element; and is ejected onto a base layer of thesubstrate for the organic light-emitting element and dried to form thefunctional layer between a first electrode included in the base layerand a second electrode opposing the base layer.

In a particular aspect of the ink pertaining to one aspect of thepresent invention, when the speed V is 3 m/s or more and is 5 m/s orless, the value Z, which is determined by the density ρ (g/m³), thesurface tension γ (mN·m), and the viscosity η (mPa·s) of the ink, is twoor more and is ten or less.

In a particular aspect of the ink pertaining to one aspect of thepresent invention, when the diameter r of the ink ejection nozzle is0.02 mm or more and is 0.03 mm or less, the density ρ of the ink is morethan 827 g/m³ and is 1190 g/m³ or less, the surface tension γ of the inkis more than 27.3 mN·m and is 41.9 mN·m or less, and the viscosity η ofthe ink is more than 2.4 mPa·s and is 35.0 mPa·s or less.

A substrate pertaining to one aspect of the present invention has thefunctional layer manufactured by using the above-mentioned ink.

An organic light-emitting element pertaining to one aspect of thepresent invention has the functional layer manufactured by using theabove-mentioned ink.

An organic display panel pertaining to one aspect of the presentinvention includes the organic light-emitting element having thefunctional layer manufactured by using the above-mentioned ink.

An organic light-emitting device pertaining to one aspect of the presentinvention includes the organic light-emitting element having thefunctional layer manufactured by using the above-mentioned ink.

An organic display device pertaining to one aspect of the presentinvention includes the organic light-emitting element having thefunctional layer manufactured by using the above-mentioned ink.

An inkjet device pertaining to one aspect of the present invention isfor containing therein ink including functional material as a materialfor a functional layer and a solvent dissolving the functional material,and ejects the ink from an ink ejection nozzle onto a substrate to formthe functional layer, the functional material having a weight-averagemolecular weight greater than zero and equal to or less than 100,000,wherein, when a value Z denotes a reciprocal of the Ohnesorge number Ohdetermined by density ρ (g/m³), surface tension γ (mN·m), and viscosityη (mPa·s) of the ink and a diameter r (mm) of the ink ejection nozzle,the value Z is within a range of the above-mentioned Formula 1, speed V(m/s) at which the ink is ejected is within a range of theabove-mentioned Formula 2, and the value Z and the speed V (m/s) satisfythe above-mentioned Formula 3.

In a particular aspect of the inkjet device pertaining to one aspect ofthe present invention, the functional material included in the ink is amaterial for the functional layer of an organic light-emitting element,and the ink is ejected onto a base layer of the substrate for theorganic light-emitting element to form the functional layer between afirst electrode included in the base layer and a second electrodeopposing the base layer.

The substrate pertaining to one aspect of the present invention has thefunctional layer manufactured by using the above-mentioned inkjetdevice.

The organic light-emitting element pertaining to one aspect of thepresent invention has the functional layer manufactured by using theabove-mentioned inkjet device.

The organic display panel pertaining to one aspect of the presentinvention includes the organic light-emitting element having thefunctional layer manufactured by using the above-mentioned inkjetdevice.

The organic light-emitting device pertaining to one aspect of thepresent invention includes the organic light-emitting element having thefunctional layer manufactured by using the above-mentioned inkjetdevice.

The organic display device pertaining to one aspect of the presentinvention includes the organic light-emitting element having thefunctional layer manufactured by using the above-mentioned inkjetdevice.

[Background Leading to Present Invention]

The inventors have perfected technology to estimate a conditionproviding preferred flight characteristics with ease and accuracythrough experiments and considerations described below.

(Considerations of Variables Used to Control Flight Characteristics)

In considering variables used to control the flight characteristics toestimate the condition providing preferred flight characteristics withease and accuracy, the inventors focused on three physical forces(viscous resistance, inertial force, and surface tension) affectingbehavior of ink.

FIG. 1 illustrates the three forces affecting the flight characteristicsof an ink drop. As illustrated in FIG. 1, the flight characteristics ofthe ink drop are determined by a balance among the three forces, thatis, the viscous resistance, the inertial force, and the surface tension.

As shown in the following Equation 1, the viscous resistance isdetermined by the viscosity η and a droplet diameter r′ of the ink, andspeed V at which the ink is ejected.Viscous force=η·r·v  (Equation 1)

As shown in the following Equation 2, the inertial force is determinedby the density ρ and the droplet diameter r′ of the ink, and theejection speed V.Inertial force=ρ·r ² ·v ²  (Equation 2)

As shown in the following Equation 3, the surface tension is determinedby the surface tension γ and the droplet diameter r′ of the ink.Surface tension=γ·r  (Equation 3)

Taken together, there are five factors affecting the flightcharacteristics of the ink drop, i.e. the density ρ, the surface tensionγ, the viscosity η, and the droplet diameter r′ of the ink, and theejection speed V. Of these five factors, four factors, that is, thedensity ρ, the surface tension γ, the viscosity η, and the dropletdiameter r′ of the ink are factors relating to the properties of theink, and only the ejection speed V is a factor other than the factorsrelating to the properties of the ink. When each of these factors isconsidered as a variable, the number of variables is as many as five. Tomake matters worse, correlations among these factors are unclear, andthis makes it extremely difficult to control the flight characteristics.

In order to facilitate control over the flight characteristics, theinventors attempted to reduce the number of variables, and, to this end,focused on the Reynolds number Nre, the Weber number Nwe, and theOhnesorge number Oh.

The Reynolds number Nre is a dimensionless number defined as the ratioof the inertial force to the viscous force, and is utilized to quantify“flow” in fluid mechanics. In the present application, the Reynoldsnumber Nre is considered to be associated primarily with thestraightness of an ink drop. As shown in the following Equation 4, theReynolds number Nre is expressed as the ratio of the inertial force tothe viscous force.Reynolds number Nre=inertial force/viscous force=v·r·ρ/η  (Equation 4)

The Weber number Nwe is a dimensionless number that is of importance intreating two-phase flow, and is utilized to analyze deformation behaviorwhen drops flow through the air and a problem of interfacial stabilityof drops. In the present application, the Weber number Nwe is consideredto be associated primarily with breakup characteristics of an ink drop.As shown in the following Equation 5, the Weber number Nwe is expressedas the ratio of the inertial force to the surface tension.Weber number Nwe=inertial force/surface tension=v ² ·r·ρ/γ  (Equation 5)

The Ohnesorge number Oh is a dimensionless number showing a relationamong the viscous force, the inertial force, and the surface tension. Asshown in the following Equation 6, the Ohnesorge number Oh is expressedas the ratio of the Reynolds number Nre to the Weber number Nwe.Ohnesorge number Oh=(Weber number Nwe)^(1/2)/Reynolds numberNre  (Equation 6)

By substituting the above-mentioned Equation 4 and Equation 5 into theabove-mentioned Equation 6, the balance among the three forces, i.e. theviscous resistance, the inertial force, and the surface tension, can beexpressed by using only four factors relating to the properties of theink, i.e. the density ρ, the surface tension γ, the viscosity η, and thedroplet diameter r′ of the ink, as shown in the following Equation 7,and the factor other than the factors relating to the properties of theink, i.e. the ejection speed V, can be eliminated. Furthermore, the fourfactors relating to the properties of the ink can collectively beexpressed by a value Z denoting a reciprocal of the Ohnesorge number Oh.

$\begin{matrix}\begin{matrix}{Z = {{1/{Ohnesorge}}\mspace{14mu}{number}\mspace{14mu}{Oh}}} \\{= {{Reynolds}\mspace{14mu}{number}\mspace{14mu}{{Nre}/( {{Weber}\mspace{14mu}{Number}\mspace{14mu}{Nwe}} )^{1/2}}}} \\{= {( \frac{{inertial}\mspace{14mu}{force}}{{viscous}\mspace{14mu}{force}} )/( \frac{{inertial}\mspace{14mu}{force}}{{surface}\mspace{14mu}{tension}} )^{1/2}}} \\{= {( {v \cdot r \cdot {\rho/\eta}} )/( {v^{2} \cdot r \cdot {\rho/\gamma}} )^{1/2}}} \\{= {( {r \cdot \rho \cdot \gamma} )^{1/2}/\eta}}\end{matrix} & ( {{Equation}\mspace{14mu} 7} )\end{matrix}$

As described above, by classifying the factors affecting the flightcharacteristics into the factor relating to the properties of the inkand the factor other than the factor relating to the properties of theink, and treating the value Z collectively expressing the factorsrelating to the properties of the ink as a single variable, the controlover the flight characteristics is facilitated.

By the above-mentioned considerations, the inventors conceived the ideaof controlling the flight characteristics by using two variables, i.e.the value Z, which expresses the factors relating to the properties ofthe ink, and the ejection speed V, which is the factor other than thefactor relating to the properties of the ink. In order to confirmcorrelations between the value Z and the flight characteristics andbetween the ejection speed V and the flight characteristics, theinventors conducted experiments. The inventors assumed that, since thevalue Z and the ejection speed V are independent of each other, thecorrelations between the value Z and the flight characteristics andbetween the ejection speed V and the flight characteristics areidentified independently.

(Correlation Between Value Z and Straightness of Ink Drop)

In order to provide preferred flight characteristics, an ink drop has tohave preferred straightness. The preferred straightness refers to astate where an ink drop ejected from the inkjet device arrives straightat a desired destination. The straightness can be evaluated, forexample, by measuring ink drop placement accuracy.

FIG. 2 illustrates the ink drop placement accuracy. The ink dropplacement accuracy is described below with use of FIG. 2.

When ink is applied by the application method using an inkjet device, aninkjet head is typically positioned above a substrate, and an ink dropis ejected downward from an ink ejection nozzle. In this case, adistance between the substrate and the inkjet head is approximately 500μm, for example.

The substrate includes, on the top surface thereof, a plurality of banks(partition walls) for partitioning light-emitting layer-forming regions(pixel units). For example, the width of each light-emittinglayer-forming region is approximately 60 μm, and the width and thethickness of each bank are approximately 30 μm and 1 μm, respectively.On the other hand, a diameter r of the ink ejection nozzle isapproximately 20 μm, and the droplet diameter r′ of the ink ejected fromthe ink ejection nozzle is approximately 24 μm. An error limit of theposition accuracy of the ink ejection nozzle is approximately ±8 μm. Itis therefore preferable to eject an ink drop with an error of ±10 μm orless, in order to eject the entire ink drop in the light-emittinglayer-forming region. In view of this, when the error is ±10 μm or less,i.e. an error of the placement accuracy is 20 μm or less, the ink dropis determined to have preferred straightness.

FIG. 3 shows experimental results on a relation between the value Z andthe placement accuracy. The value Z was controlled by changingfunctional material and a solvent included in ink, the concentration(the concentration of the functional material in the ink), the viscosityη, the surface tension γ, and the density ρ of the ink, and the diameterr of the ink ejection nozzle. Ink drops were ejected on the conditiondescribed with use of FIG. 2, and then the ink drop placement accuracywas measured and evaluated by using standard deviation 6σ. The dropletdiameter r′ of the ink depends on the diameter r of the ink ejectionnozzle, and thus the diameter r is used instead of using the dropletdiameter r′ of the ink.

In order to evaluate ink including functional material having aweight-average molecular weight greater than zero and equal to or lessthan 100,000 (abbreviated as “100 k” in the figures of the presentapplication), the experiments were conducted by using ink includingfunctional material having a weight-average molecular weight of 100,000.The experiments were also conducted by using, as an alternative to inkincluding functional material having a weight-average molecular weightthat is as close to zero as possible, ink including functional materialhaving a weight-average molecular weight of zero, i.e. ink not includingfunctional material (a solvent alone).

In the column of “solvent” in FIG. 3, solvents A, B, C, D, E, F, G, H,I, J, and K respectively indicate 1-nonanol, dimethyl phthalate,xylene/1-nonanol=14/86, dimethyl phthalate/1-nonanol=50/50,acetophenone/dimethyl phthalate=17/83, xylene/dimethyl phthalate=25/75,xylene/1-nonanol=35/65, acetophenone/dimethyl phthalate=50/50,xylene/1-nonanol=50/50, xylene/dimethyl phthalate=50/50, andcyclohexylbenzene.

For example, on the condition shown as No. 1, an error of the placementaccuracy is 11.3 μm, which is within 20 μm. In this case, the results ofthe judgment are indicated by a circle (∘), which indicates that thepreferred straightness can be obtained. On each of the other conditions,an error of the placement accuracy is 20 μm or less. In this case, theresults of the judgment are indicated by a circle (∘), which indicatesthat the preferred straightness can be obtained.

FIG. 4 shows the relation between the value Z and the placementaccuracy. When the experimental results No. 1 to No. 20 shown in FIG. 3are plotted in the X and Y coordinates showing the value Z on the X axisand showing the placement accuracy on the Y axis as shown in FIG. 4, itis found that there is a correlation between the value Z and a satellitegeneration speed. It is also found that the placement accuracy isdegraded as the value Z decreases, and, when the value Z is less than0.7, an error of the placement accuracy exceeds 20 μm. In view of this,a lower limit of the value Z is determined as 0.7. Furthermore, as isapparent from a slope of an approximate curve shown in FIG. 4, it isconsidered desirable that the value Z be two or more in terms of thestability of the preferred placement accuracy.

It was found that one of the causes of the degradation of the placementaccuracy is an increase in the ligament length when the value Z is smalland the viscosity of the ink is high, because an ink drop is less likelyto break off from the ink ejection nozzle in such a case. It was alsofound that the preferred placement accuracy was obtained when theviscosity η of the ink is low, because the ink drop is more likely tobreak off and thus the ligament is short in such a case.

(Correlation between Ejection Speed V and Straightness of Ink Drop)

The correlation between the ejection speed V and the flightcharacteristics was examined by investigating the relation between theejection speed V and the straightness of an ink drop (placementaccuracy). Ink used for measurement includes F8-F6 as functionalmaterial, and includes any of cyclohexylbenzene, methoxytoluene,1-nonanol, dimethyl phthalate, acetophenone, and xylene as a solvent.Various types of ink were ejected from the ink ejection nozzle whilechanging the ejection speed V. The placement accuracy is then measuredand evaluated by using the standard deviation 6σ. The ejection speed Vwas obtained by measuring the speed of a drop of 0.5 mm ejected from theinkjet head by using Litrex 120L, which is an inkjet evaluation devicemanufactured by ULVAC, Inc.

FIG. 5 shows a relation between the ejection speed V and the placementaccuracy. The results shown in FIG. 5 were obtained by the measurement.The results indicate that there is a correlation between the ejectionspeed V and the placement accuracy, and the preferred placement accuracyis obtained when the ejection speed V is a predetermined speed or more.Presumably, this is because the ink drop becomes less likely to becarried by air currents as the ejection speed V increases. It was foundthat, when the ejection speed V was 3 m/s or more, the placementaccuracy did not exceed an allowable limit of 20 μm, even with a smallerror. A lower limit of the preferred ejection speed V was thusdetermined as 3 m/s.

It was also found that the types of solvent had little effect on therelation between the ejection speed V and the placement accuracy.

FIG. 6 shows a relation between the ejection speed V and a variation ofthe ejection speed. The graph of FIG. 6 shows the ejection speed V onthe X axis and shows, on the Y axis, a value obtained by dividing thestandard deviation of the ejection speed by an average value of theejection speed V. As shown in FIG. 6, it is considered that, when theejection speed V is 3 m/s or more and is 5 m/s or less, the value shownon the Y axis is 2% or less and an ink drop is less likely to beaffected by air currents. It is therefore preferable that the ejectionspeed V be 3 m/s or more and is 5 m/s or less.

(Correlation between Ejection Speed V and Breakup Characteristics of InkDrop)

In the above-mentioned experiments, it was also found that, when theejection speed V was increased, the ink drop broke up to generatesatellites and the flight characteristics were degraded. In order toprovide the preferred flight characteristics for an ink drop, the inkdrop has to have preferred breakup characteristics. The preferredbreakup characteristics of the ink drop refer to a state where the inkdrop does not break up.

FIGS. 7A, 7B, 7C, and 7D illustrate examples of how an ink drop breaksup. As one example of how the ink drop breaks up, there is a case wherethe ink drop breaks up into a few small drops. In the example shown inFIG. 7A, the ink drop breaks up into two small drops A and B. If the inkdrop breaks up as shown in FIG. 7A, it is not possible to control theejection because determination of a main drop is not possible. Asanother example of how the ink drop breaks up, there is a case where theink drop breaks up into a main drop and a plurality of satellites (smalldrops separated from the main drop). In the example shown in FIG. 7B,the ink drop breaks up into a main drop C and a plurality of satellitesD. If the ink drop breaks up as shown in FIG. 7B, any of the satellitesmight be placed in a region other than the light-emitting layer-formingregion. In view of above, an ink drop was determined to have preferredbreakup characteristics when the ink drop did not break up.

In order to improve visual understanding of how the ink drop breaks up,schematic diagrams for images shown in FIGS. 7A and 7B are respectivelyshown in FIGS. 7C and 7D.

The breakup characteristics were evaluated in the following manner. Thebreakup characteristics were evaluated by observing the flight of an inkdrop to judge whether or not the ink drop breaks up. The flight of theink drop was observed to examine a shape of the ejected ink drop withresolution of 1 usec by using Litrex 120L, which is the inkjetevaluation device manufactured by ULVAC, Inc.

When the ejection speed V exceeded 6 m/s, satellites were generated andthus the placement accuracy could not accurately be measured. An upperlimit of the ejection speed V is therefore determined as 6 m/s.

The correlation between the ejection speed V and the flightcharacteristics is summarized as follows: When the ejection speed V islow, the preferred breakup characteristics is obtained (ink is lesslikely to break up) but the preferred straightness cannot be obtained.On the other hand, when the ejection speed V is high, the preferredstraightness is obtained but the preferred breakup characteristicscannot be obtained (ink is more likely to break up). A preferred rangeof the ejection speed V is 3 m/s or more and is 6 m/s or less. Asdescribed above, the inventors found that, in addition to thestraightness, the breakup characteristics were important (to preventgeneration of satellites) for the flight characteristics.

(Correlation between Value Z and Breakup Characteristics of Ink Drop)

From the initial consideration, it was considered that the flightcharacteristics could sufficiently be controlled by conducting theexperiments to find variables for the value Z and the ejection speed Vand obtaining a formula indicating the correlation therebetween.However, since it was found that there was the upper limit of theejection speed V from the perspective of the breakup characteristics ofthe ink drop, the inventors assumed that there would be some correlationbetween the value Z and the breakup characteristics of the ink drop, andfurther proceeded to a consideration.

At first, the inventors roughly considered the correlation between thevalue Z and the satellite generation speed without regard to theweight-average molecular weight. The satellite generation speed refersto an ejection speed at and above which a satellite is generated, andsets the upper limit to obtain the preferred flight characteristicsdetermined by the value Z for each ink drop.

FIG. 8 shows the relation between the value Z and the satellitegeneration speed. FIGS. 9A and 9B illustrate examples of an ink drop inan area I of FIG. 8. FIGS. 10A and 10B illustrate examples of an inkdrop in an area II of FIG. 8. FIGS. 11A and 11B illustrate examples ofan ink drop in an area III of FIG. 8.

The viscosity η of ink was measured by using a viscometer referred to asAR-G2 (TA Instruments). The surface tension γ of ink was measured byusing a surface tension meter referred to as DSA100 (manufactured byKRUSS). The density ρ of ink was calculated from the specific gravity ofthe ink (since the functional material has a low concentration, thespecific gravity thereof is assumed to be one).

As shown in FIG. 8, there was a correlation between the value Z and thesatellite generation speed. As shown in FIG. 9A, in the area I of FIG.8, a satellite was not generated when the viscosity η of the ink wasapproximately 15 mPa·s and when the viscosity η of the ink wasapproximately 1 mPa·s. The area I is thus a normal area where ink dropsare ejected one at a time. As shown in FIG. 10A, in the area II of FIG.8, when the viscosity η of the ink was approximately 15 mPa·s, theligament length of an ink drop increased (a phenomenon where the inkleaves a trail), and the ink drop broke up. When the viscosity 11 of theink was approximately 1 mPa·s, however, the ink drop did not break up.As shown in FIG. 11A, in the area III of FIG. 8, satellites weregenerated when the viscosity η of the ink was approximately 15 mPa·s andwhen the viscosity η of the ink was approximately 1 mPa·s.

In order to improve visual understanding of how the ink drop breaks up,schematic diagrams of images shown in FIGS. 9A, 10A, and 11A arerespectively shown in FIGS. 9B, 10B, and 11B.

The correlation between the value Z and the satellite generation speedwas then considered in detail. The value Z was controlled by changingfunctional material and a solvent included in ink, the concentration (aratio of the functional material to the ink), the viscosity η, thesurface tension γ, and the density ρ of the ink, and the nozzle diameterr at a level shown in the table. Ink drops were ejected on the conditiondescribed with use of FIG. 2 to measure an ejection speed V at whichsatellites are generated. The droplet diameter r′ of the ink depends onthe diameter r of the ink ejection nozzle, and thus the diameter r isused instead of using the droplet diameter r′ of the ink.

In order to evaluate the ink including functional material having aweight-average molecular weight greater than zero and equal to or lessthan 100,000, the experiments were conducted by using the ink includingfunctional material having a weight-average molecular weight of 100,000and the ink including functional material having a weight-averagemolecular weight of zero (ink not including functional material).

FIG. 12 shows experimental results on the relation between the value Zand the satellite generation speed. For example, in the case of No. 21of FIG. 12, in which the value Z is 15.0, a satellite was generated whenthe ejection speed V was 2.7 m/s or more. In the case of No. 22, inwhich the value Z is 33.8, a satellite was generated when the ejectionspeed V was 0.9 m/s or more.

As described above, in order to keep an error of the placement accuracyequal to 20 μm or less, it is preferred that the ejection speed V be 3.0m/s or more. In the case of No. 21, in which the satellite generationspeed is 2.7 m/s, however, a satellite might be generated when theejection speed V is 2.7 m/s or more. That is to say, in the case of No.21, it is not possible to provide both of the preferred straightness andbreakup characteristics. No. 21 was therefore evaluated as “x”, whichindicates that the preferred breakup characteristics cannot be obtained.Similarly, cases in each of which the satellite generation speed was 3.0m/s or less were evaluated as “x”, which indicates that the preferredbreakup characteristics cannot be obtained. In contrast, cases in eachof which the satellite generation speed exceeded 3.0 m/s were evaluatedas “∘”, which indicates that the preferred breakup characteristics canbe obtained.

In the column of “solvent” in FIG. 12, solvents a, b, c, d, e, f, g, h,i, j, k, l, and m respectively indicate acetophenone, xylene,xylene/1-nonanol=14/86, dimethyl phthalate/1-nonanol=50/50,acetophenone/dimethyl phthalate=17/83, xylene/dimethyl phthalate=25/75,xylene/1-nonanol=35/65, acetophenone/dimethyl phthalate=50/50,acetophenone/dimethyl phthalate=78/22, xylene/dimethyl phthalate=50/50,xylene/dimethyl phthalate=85/15, methoxytoluene, and cyclohexylbenzene.

FIG. 13 shows the relation between the value Z and the satellitegeneration speed. When the experimental results No. 21 to No. 40 shownin FIG. 12 were plotted in the X and Y coordinates showing the value Zon the X axis and showing the satellite generation speed on the Y axisas shown in FIG. 13 to perform regression analysis, a regressionequation as shown in the following Equation 8 was obtained, and it wasfound that there was a correlation between the value Z and the satellitegeneration speed. This means that speed at which satellites aregenerated can be estimated from the value Z.y=−2.17 Ln(x)+8.47  (Equation 8)

In the graph of FIG. 13, an area below the regression line is an area inwhich satellites are not generated. It can be seen from the graph thatthe satellite generation speed falls below 3.0 m/s when the value Zexceeds 13. An upper limit of the value Z is therefore determined as 13.

(Summary)

As described above, it was found that the breakup characteristics of theink drop did not depend only on the ejection speed V but depended on thevariables for both of the ejection speed V and the value Z, and, inorder to provide preferred breakup characteristics of the ink drop, itwas important for the value Z and the ejection speed V to show apredetermined relation.

The inventors could arrive at the present invention by determining anunanticipated correlation existing between the value Z and the ejectionspeed V, which were each assumed to be independently defined at thebeginning of the considerations.

FIG. 14 shows relations between the value Z and the satellite generationspeed (FIG. 13), and between the value Z and the placement accuracy(FIG. 4). In the graph of FIG. 14, a hatched range indicates a range ofthe value Z within which the preferred placement accuracy is providedand satellites are not generated, i.e., a range of the value Z withinwhich the preferred flight characteristics can be obtained. When thevalue Z is increased, for example, by increasing the viscosity of theink, the preferred breakup characteristics can be obtained (the ink isless likely to break up) but the straightness is degraded. On the otherhand, when the value Z is decreased, the breakup characteristics aredegraded (the ink is more likely to break up) but the preferredstraightness can be obtained.

As described above, the inventors demonstrated by the experiments thatthe flight characteristics of the ink drop could be controlled by thevalue Z, and there was a correlation between the flight characteristicsof the ink drop and the value Z. That is to say, the inventors succeededin making the properties of the ink capable of providing the preferredflight characteristics predictable according to the inkjet head to beused, and in controlling the flight characteristics of the ink drop bygeneralizing a relation between the flight characteristics of the inkdrop and the value Z for the ink drop, which is determined by theviscosity η, the surface tension γ, the density ρ of the ink, and thediameter r of the ink ejection nozzle. This allowed for reduction of theburden in development of ink and ejection evaluation.

Furthermore, by defining the ejection speed V, the relation between theejection speed V and the flight characteristics could be grasped moreaccurately. This lead to optimal design of ink according to the inkejection nozzle of the inkjet device. The inventors found that thepreferred flight characteristics could be obtained by controlling thevalue Z and the ejection speed V so that the above-mentioned Formula 1,Formula 2, and Formula 3 are satisfied. When the value Z is two or moreand is ten or less, more preferred flight characteristics can beobtained.

[Ink]

The ink pertaining to one aspect of the present invention includesfunctional material as a material for a functional layer and a solventdissolving the functional material, and has properties suitable for theinkjet method using the inkjet device (drop ejection method). As can beseen from FIGS. 3 and 12, it is preferred that the density ρ of the inkbe more than 827 g/m³ and be 1190 g/m³ or less, the surface tension γ ofthe ink be more than 27.3 mN·m and be 41.9 mN·m or less, and theviscosity η of the ink be 2.4 mPa·s or more and be 35.0 mPa·s or less.In this case, it is preferred that the diameter r of the ink ejectionnozzle of the inkjet device be 0.02 mm or more and be 0.03 mm or less.

Specifically, F8-F6 (a copolymer of F8 (poly dioctyifluorene) and F6(poly dihexylfluorene)) is preferred for use as the functional material.Other materials preferred for use as the functional material are afluorene compound other than F8-F, such as F8 and F6, an oxinoidcompound, a perylene compound, a coumarin compound, an azacoumarincompound, an oxazole compound, an oxadiazole compound, a perinonecompound, a pyrrolo-pyrrole compound, a naphthalene compound, ananthracene compound, a fluoranthene compound, a tetracene compound, apyrene compound, a coronene compound, a quinolone compound and anazaquinolone compound, a pyrazoline derivative and a pyrazolonederivative, a rhodamine compound, a chrysene compound, a phenanthrenecompound, a cyclopentadiene compound, a stilbene compound, adiphenylquinone compound, a styryl compound, a butadiene compound, adicyanomethylene pyran compound, a dicyanomethylene thiopyran compound,a fluorescein compound, a pyrylium compound, a thiapyrylium compound, aselenapyrylium compound, a telluropyrylium compound, an aromaticaldadiene compound, an oligophenylene compound, a thioxanthene compound,an anthracene compound, a cyanine compound, an acridine compound, ametal complex of a 8-hydroxyquinoline compound, a metal complex of a2-bipyridine compound, a complex of a Schiff base and a group threemetal, a metal complex of oxine, a rare earth metal complex, etc., asrecited in Japanese Patent Application Publication No. 5-163488. Thesecompounds and complexes may be used alone, or one or more of thesecompounds and complexes may be used in combination.

In the present application, the above-mentioned experiments on thecorrelations between the value Z and the flight characteristics, andbetween the ejection speed V and the flight characteristics wereconducted by using functional material having a weight-average molecularweight greater than zero and equal to or less than 100,000. Thefunctional material having a weight-average molecular weight greaterthan zero and equal to or less than 100,000 is preferably used for inkfor forming a light-emitting functional layer that emits red or greenlight, for example. The light-emitting functional layer that emits greenlight has a film thickness of 60 nm to 100 nm, for example. In order toobtain ink having a concentration suitable for designing thelight-emitting functional layer having such a film thickness, it ispreferred to use functional material having a weight-average molecularweight greater than zero and equal to or less than 100,000. It is morepreferred to use functional material having a weight-average molecularweight equal to or greater than 80,000 and equal to or less than100,000. When F8-F6 is used as the functional material, a minimum valueof the weight-average molecular weight thereof is theoretically 722.

FIG. 15 shows a relation among the value Z, the concentration of ink,and the viscosity η of the ink. The value Z, the concentration of theink, and the viscosity η of the ink shown in FIG. 15 are obtained whenF8-F6 is used as functional material, and a mixture of cyclohexylbenzeneand methoxytoluene is used as a solvent (with a mixing ratio ofcyclohexylbenzene to methoxytoluene is 8:2). In the case of thefunctional material having a weight-average molecular weight greaterthan zero and equal to or less than 100,000, a preferred range of theconcentration (wt/vol) of the ink is 0.5% or more and is 3.0% or less, apreferred range of the viscosity η of the ink is 4.5 mPa·s or more andis 28.0 mPa·s or less, and a preferred range of the value Z is 0.9 ormore and is 6.0 or less.

When F8-F6 is used as the functional material, it is preferred to usecyclohexylbenzene, methoxytoluene, methylnaphthalene, xylene, or thelike as the solvent. The solvent may include a single material or may bea mixture of a plurality of materials as long as the solvent candissolve the functional material.

[Organic Display Panel, Organic Light-emitting Element, and Substrate]

FIG. 16 is a schematic diagram illustrating a laminated structure oflayers included in an organic display panel pertaining to one aspect ofthe present invention. As illustrated in FIG. 16, an organic displaypanel 110 pertaining to one aspect of the present invention has astructure in which a color filter substrate 113 is bonded onto anorganic light-emitting element 111 pertaining to one aspect of thepresent invention via a sealing material 112.

The organic light-emitting element 111 is a top emission-type organiclight-emitting element in which the pixels for the colors R, G and B arearranged in a matrix or in lines, and each pixel has a laminatedstructure composed of layers formed on a TFT substrate 1.

On the TFT substrate 1, first anode electrodes 2 and second anodeelectrodes 3 constituting a first electrode are formed in a matrix or inlines. On the anode electrodes 2 and 3, a hole injection layer 4 isformed. On the hole injection layer 4, banks 5 for defining pixels areformed.

A substrate 11 pertaining to one aspect of the present inventionincludes the TFT substrate 1, the anode electrodes 2 and 3, and thebanks 5, and has openings 12 corresponding to respective pixel units.The banks 5 are each formed above the anode electrodes 2 and 3 topartition adjacent pixel units.

In an area defined by the banks 5, a hole transport layer 6 and anorganic light-emitting layer 7 are formed in the stated order. On theorganic light-emitting layer 7, an electron transport layer 8, a cathodeelectrode 9 as a second electrode, and a passivation layer 10 are formedcontinuously across adjacent pixels, passing over the banks 5.

The area defined by the banks 5 has a multi-layered structure in whichthe hole injection layer 4, the hole transport layer 6, the organiclight-emitting layer (functional layer) 7, and the electron transportlayer 8 are formed in the stated order.

The multi-layered structure may include another layer such as anelectron injection layer. Typical examples of the multi-layeredstructure include: (i) the hole injection layer/the organiclight-emitting layer; (ii) the hole injection layer/the hole transportlayer/the organic light-emitting layer; (iii) the hole injectionlayer/the organic light-emitting layer/the electron injection layer;(iv) the hole injection layer/the hole transport layer/the organiclight-emitting layer/the electron injection layer; (v) the holeinjection layer/the organic light-emitting layer/a hole blockinglayer/the electron injection layer; (vi) the hole injection layer/thehole transport layer/the organic light-emitting layer/the hole blockinglayer/the electron injection layer; (vii) the organic light-emittinglayer/the hole blocking layer/the electron injection layer; and (viii)the organic light-emitting layer/the electron injection layer.

The TFT substrate 1 includes a base substrate and an amorphous TFT (anEL element drive circuit) formed on the base substrate. The basesubstrate is, for example, made of an insulating material such asalkali-free glass, soda glass, nonfluorescent glass, phosphate glass,borate glass, quartz, acrylic resin, styrenic resin, polycarbonateresin, epoxy resin, polyethylene, polyester, silicone resin, andalumina.

The first anode electrode 2 is made, for example, of Ag (silver), APC(alloy of silver, palladium, and copper), ARA (alloy of silver, rubidiumand, gold), MoCr (alloy of molybdenum and chromium), or NiCr (alloy ofnickel and chromium). In the case of a top emission-type organiclight-emitting element, it is preferred that the first anode electrode 2be made of a light reflective material.

The second anode electrode 3 is interposed between the first anodeelectrode 2 and the hole injection layer 4, and has a function toenhance bonding therebetween.

It is preferred that the hole injection layer 4 be made of a metalcompound such as a metal oxide, a metal nitride, or a metal oxynitride.When the hole injection layer 4 is made of a metal oxide, injection ofholes is facilitated. Accordingly, electrons injected into the organiclight-emitting layer 7 contribute to light emission in an effectivemanner, which results in excellent light-emitting characteristics of theorganic light-emitting layer 7. Examples of the metal oxide includeoxides of: Cr (chromium); Mo (molybdenum); W (tungsten); V (vanadium);Nb (niobium); Ta (tantalum); Ti (titanium); Zr (zirconium); Hf(hafnium); Sc (scandium); Y (yttrium); Th (thorium); Mn (manganese); Fe(iron); Ru (ruthenium); Os (osmium); Co (cobalt); Ni (nickel); Cu(copper); Zn (zinc); Cd (cadmium); Al (aluminum); Ga (gallium); In(indium); Si (silicon); Ge (germanium); Sn (tin); Pb (lead); Sb(antimony); Bi (bismuth); and so-called rare earth elements from La(lanthanum) to Lu (lutetium). Among such metal oxides, Al₂O₃ (aluminumoxide), CuO (copper oxide), and SiO (silicon oxide) are particularlyefficient in extending the life of the light-emitting element.

It is preferred that the banks 5 be made of an organic material such asa resin, or an inorganic material such as glass. Examples of the organicmaterial are an acrylic resin, a polyimide resin, and a novolac typephenolic resin. Examples of the inorganic material are SiO, (siliconoxide) and Si₃N₄ (silicon nitride). It is preferred that the banks 5 beresistant to organic solvents, transmit visible light to some extent,and have insulating properties. In addition, since there are cases wherethe banks 5 undergo etching, baking and other similar processing, it ispreferred that the banks 5 be made of a material that is highlyresistant to such processing.

The banks 5 may be pixel banks or line banks. When the banks 5 are thepixel banks, the banks 5 are formed so as to surround the organiclight-emitting layer 7 corresponding to one pixel from all directions.When the banks 5 are the line banks, the banks 5 are formed so as topartition pixels by columns or by rows. The banks 5 exist at both sidesof the organic light-emitting layer 7 in either the row direction or inthe column direction, and the organic light-emitting layer 7 is formedso as to be continuous in either the column direction or the rowdirection.

The hole transport layer 6 has a function to transport holes injectedfrom the anode electrodes 2 and 3 to the organic light-emitting layer 7.It is preferred that the hole transport layer 6 be made ofpoly(3,4-ethylenedioxythiophene) doped with polystyrene sulphonate(PEDOT-PSS), or a derivative (copolymer or the like) thereof.

The organic light-emitting layer 7 has a function to emit light bymaking use of the phenomenon of electroluminescence. It is preferredthat the organic light-emitting layer 7 be made, for example, of thefunctional material included in the ink pertaining to one aspect of thepresent invention.

The electron transport layer 8 has a function to transport electronsinjected from the cathode electrode 9 to the organic light-emittinglayer 7. It is preferred that the electron transport layer 8 be made,for example, of barium, phthalocyanine, lithium fluoride, or a mixtureof any of these materials.

The cathode electrode 9 is made, for example, of ITO or IZO (Indium ZincOxide). In the case of the top emission-type organic light-emittingelement, it is preferred that the passivation layer 10 be made of alight-transmissive material.

The passivation layer 10 has a function to prevent the organiclight-emitting layer 7 and the like from being exposed to moisture orair, and is made, for example, of SiN (silicon nitride) or SiON (siliconoxynitride). In the case of the top emission-type organic light-emittingelement, it is preferred that the passivation layer 10 be made of alight-transmissive material.

The organic light-emitting element 111 and the organic display panel 110having the above-described structure has excellent light-emittingcharacteristics, as they are manufactured by using a method ofmanufacturing an organic light-emitting element pertaining to one aspectof the present invention.

[Inkjet Device and Method of Manufacturing Organic Light-EmittingElement]

The following describes an inkjet device and a method of manufacturingan organic light-emitting element pertaining to one aspect of thepresent invention with use of FIGS. 17, 18A to 18G, and 19A to 19E. FIG.17 illustrates a structure of an inkjet device pertaining to one aspectof the present invention. FIGS. 18A to 18G and 19A to 19E are a processchart showing the method of manufacturing the organic light-emittingelement pertaining to one aspect of the present invention.

The method of manufacturing the organic light-emitting elementpertaining to one aspect of the present invention includes five steps.

In the first step, ink pertaining to one aspect of the present inventionis prepared and a common ink chamber 21 of an inkjet device 20pertaining to one aspect of the present invention is filled with theink, as illustrated in FIG. 17. The ink includes functional material 22.

The ink filling the common ink chamber 21 is transported to a pressuregeneration chamber 24 through an ink common path 23. The wall of thepressure generation chamber 24 partially includes a vibrating plate 25.By heating the vibrating plate 25 with a heater 26 to cause thevibrating plate 25 to vibrate in directions indicated by an arrow, thepressure generation chamber 24 expands and contracts. By pressuregenerated by the expansion and contraction of the pressure generationchamber 24, a drop 28 of the ink is ejected from an ink ejection nozzle27.

In the second step, the substrate 11 having a base layer including thefirst electrodes 2 and 3 is prepared to form the organic light-emittinglayer 7.

Specifically, the TFT substrate 1 is prepared first. As illustrated inFIG. 18A, an upper surface of the TFT substrate 1 is protected by aprotective resist.

The protective resist covering the TFT substrate 1 is then removed asillustrated in FIG. 18B. By spin-coating the TFT substrate 1 with anorganic resin, and patterning the spin-coated TFT substrate 1 by PR/PE(photoresist/photoetching), a planarizing film 1 a (having a thicknessof 4 μm, for example) is formed as illustrated in FIG. 18C.

As illustrated in FIG. 18D, the first anode electrodes 2 are then formedon the planarizing film 1 a. The first anode electrodes 2 are formed,for example, by forming a thin film of APC by sputtering, and then bypatterning the thin film by PR/PE in a matrix (so as to have a thicknessof 150 nm, for example). The first anode electrodes 2 may be formed by avacuum deposition method or the like.

As illustrated in FIG. 18E, the second anode electrodes 3 are formed ina matrix. The second anode electrodes 3 are formed, for example, byforming a thin film of ITO by plasma deposition, and then by patterningthe ITO thin film by PR/PE (so as to have a thickness of 110 nm, forexample).

As illustrated in FIG. 18F, the hole injection layer 4 is formed overthe second anode electrodes 3. The hole injection layer 4 is formed, forexample, by sputtering a material for achieving a hole injectionfunction, and then by patterning the material by PR/PE (so as to have athickness of 40 nm, for example). The hole injection layer 4 is formednot only on the anode electrodes 3 but also over the entire uppersurface of the TFT substrate 1.

As illustrated in FIG. 18G, the banks 5 are then formed on the holeinjection layer 4. Areas on the hole injection layer 4 in which thebanks 5 are formed correspond to boundaries between adjacentlight-emitting layer-forming regions. The banks 5 are formed by forminga bank material layer so as to cover the entire upper surface of thehole injection layer 4, and then by removing parts of the bank materiallayer by PR/PE (so as to have a thickness of 1 μm, for example). Thebanks 5 may be line banks arranged in stripes extending only in thevertical direction, or may be pixel banks extending both in the verticaland horizontal directions to be in a lattice shape as a whole in a planview.

As shown in FIG. 19A, each concavity formed between the banks 5 isfilled with ink including a material for the hole transport layer andthe ink is dried to form the hole transport layer 6 (having a thicknessof 20 nm, for example).

In the third step, as illustrated in FIG. 19B, the inkjet device 20 ispositioned above the substrate 11, and is caused to eject a drop of theink onto the hole injection layer 4 in regions corresponding to theopenings 12 between the banks 5.

In the fourth step, the ink filling each concavity is dried underreduced pressure and baked to form the organic light-emitting layer 7(having a thickness of 60 nm to 90 nm, for example).

As illustrated in FIG. 19C, the electron transport layer 8 (having athickness of 20 nm) is then formed to cover the banks 5 and the organiclight-emitting layer 7 by ETL deposition.

In the fifth step, as illustrated in FIG. 19D, the second electrode 9,which has a different polarity from the first electrodes 2 and 3, isformed above the organic light-emitting layer 7 by plasma deposition ofa light-transmissive material (so as to have a thickness of 100 nm).

As illustrated in FIG. 19E, the passivation layer 10 is then formed onthe cathode electrode 9 by CVD (so as to have a thickness of 1 μm).

The top emission-type organic light-emitting element is manufactured inthe above-mentioned manner.

[Organic Display Device]

FIG. 20 is a perspective view illustrating an organic display devicepertaining to one aspect of the present invention and the like. Asillustrated in FIG. 20, a display device 100 pertaining to one aspect ofthe present invention is an organic EL display formed by regularlyarranging pixels each emitting light of R, G, or B color in the columnand the row directions so as to form a matrix. Each of the pixelsincludes the organic EL element pertaining to one aspect of the presentinvention.

FIG. 21 illustrates an overall structure of the organic display devicepertaining to one aspect of the present invention. As illustrated inFIG. 21, the organic display device 100 includes the organic displaypanel 110 pertaining to one aspect of the present invention and a drivecontrol unit 120 connected to the organic display panel 110. The drivecontrol unit 120 includes four drive circuits 121 to 124 and a controlcircuit 125. In the organic display device 100 actually implemented, thearrangement of the drive control unit 120 relative to the organicdisplay panel 110 and the connection between the drive control unit 120and the organic display panel 110 are not limited to those describedabove.

The organic display device 100 having the above-mentioned structureprovides excellent image quality, as it utilizes the organiclight-emitting element having excellent light-emitting characteristics.

[Organic Light-emitting Device]

FIGS. 22A and 22B are respectively a vertical cross-sectional view and ahorizontal cross-sectional view of the organic light-emitting devicepertaining to one aspect of the present invention. As illustrated inFIGS. 22A and 22B, an organic light-emitting device 200 includes: aplurality of organic light-emitting elements 210 pertaining to oneaspect of the present invention; a base 220 having the organiclight-emitting elements 210 mounted on an upper surface thereof; and apair of reflection members 230 attached to the base 220 so as tosandwich the organic light-emitting elements 210. Each of the organiclight-emitting elements 210 is electrically connected to an electricallyconductive pattern (not illustrated) formed on the base 220, and emitslight by driving power provided by the electrically conductive pattern.The reflection members 230 control distribution of a portion of lightemitted from the organic light-emitting elements 210.

The organic light-emitting device 200 having the above-mentionedstructure provides excellent image quality, as it utilizes the organiclight-emitting element having excellent light-emitting characteristics.

[Modifications]

Specific explanation has been provided of the method of manufacturingthe organic light-emitting element, the organic display panel, theorganic light-emitting device, the method of forming the functionallayer, the ink, the substrate, the organic light-emitting element, theorganic display device, and the inkjet device pertaining to one aspectof the present invention. It should be noted, however, that theabove-mentioned embodiment is merely one example used to describe theeffects of the structure of the present invention, and therefore, thepresent invention should not be construed as being limited to theabove-mentioned embodiment.

For example, the ink for the organic light-emitting element pertainingto one aspect of the present invention is not limited to the ink forforming the organic light-emitting layer, and may be ink for forming afunctional layer other than the organic light-emitting layer, such asthe hole transport layer, the electron transport layer, the holeinjection layer, and the electron injection layer.

The organic light-emitting element pertaining to one aspect of thepresent invention is not limited to the top emission-type organiclight-emitting element, and may be the bottom emission-type organiclight-emitting element.

Regarding the organic display panel pertaining to one aspect of thepresent invention, although the color of light emitted from the organiclight-emitting layer is not referred to in the above-mentionedembodiment, the organic display panel may achieve not only monochromedisplay but also full color display. In the organic display panel thatachieves full color display, the organic light-emitting elementcorresponds to one sub-pixel for each of the colors R, G and B, and acombination of three adjacent sub-pixels for the colors R, G, and B formone pixel. A plurality of such pixels are arranged in a matrix to forman image display region of the organic display panel.

The ink pertaining to one aspect of the present invention is not limitedto the ink for the organic light-emitting element and may be ink for anorganic transistor element.

INDUSTRIAL APPLICABILITY

The ink for the organic light-emitting element pertaining to one aspectof the present invention is widely applicable to a process ofmanufacturing the organic light-emitting element by a wet process. Inaddition, the organic light-emitting element pertaining to one aspect ofthe present invention is widely applicable in, for example, the field ofpassive matrix-type and active matrix-type organic display devices andorganic light-emitting devices.

REFERENCE SIGNS LIST

-   -   2, 3 first electrode    -   5 bank    -   6 functional layer    -   9 second electrode    -   11 substrate    -   12 opening    -   20 inkjet device    -   22 functional material    -   27 ink ejection nozzle    -   100 organic light-emitting device    -   110 organic display panel    -   111 organic light-emitting element    -   200 organic display device

The invention claimed is:
 1. A method of manufacturing an organiclight-emitting element, comprising: preparing ink including functionalmaterial as a material for a functional layer and a solvent dissolvingthe functional material, and filling an inkjet device having an inkejection nozzle with the ink, the functional material having aweight-average molecular weight greater than zero and equal to or lessthan 100,000; preparing a substrate having a base layer including afirst electrode; positioning the inkjet device above the substrate, andcausing the inkjet device to eject a drop of the ink onto the base layerof the substrate; forming the functional layer by drying the ink ejectedonto the base layer of the substrate; and forming a second electrodeabove the functional layer, wherein in the preparation of the ink, whena value Z denotes a reciprocal of the Ohnesorge number Oh determined bydensity ρ (g/m³), surface tension γ (nM·m), and viscosity η (mPa·s) ofthe ink and a diameter r (mm) of the ink ejection nozzle, the value Z iswithin a range of Formula 1, in the ejection of the drop of the ink,speed V (m/s) of the ejected drop of the ink is within a range ofFormula 2, and the value Z and the speed V (m/s) satisfy Formula 3:0.7≦Z≦13where Z=1/Ohnesorge number Oh=(r·ρ·γ)^(1/2)/η  (Formula 1);3≦V≦6  (Formula 2); andV≦−2.17 Ln(Z)+8.47  (Formula 3).
 2. The method of manufacturing theorganic light-emitting element of claim 1, wherein the value Z is two ormore and is ten or less, and the speed V is 3 m/s or more and is 5 m/sor less.
 3. The method of manufacturing the organic light-emittingelement of claim 1, wherein the density ρ of the ink is more than 827g/m³ and is 1190 g/m³ or less, the surface tension γ of the ink is morethan 27.3 mN·m and is 41.9 mN·m or less, the viscosity η of the ink ismore than 2.4 mPa·s and is 35.0 mPa·s or less, and the diameter r of theink ejection nozzle is 0.02 mm or more and is 0.03 mm or less.
 4. Themethod of manufacturing the organic light-emitting element of claim 1,wherein in the preparation of the substrate, the substrate has aplurality of openings corresponding to respective pixel units andincludes a plurality of banks each formed above the base layer topartition adjacent pixel units, and in the ejection of the drop of theink, drops of the ink are ejected onto the base layer in regionscorresponding to the openings between the banks.
 5. An organic displaypanel utilizing the organic light-emitting element manufactured by themethod of claim
 1. 6. An organic light-emitting device utilizing theorganic light-emitting element manufactured by the method of claim
 1. 7.An organic display device utilizing the organic light-emitting elementmanufactured by the method of claim
 1. 8. A method of forming afunctional layer, comprising: preparing ink including functionalmaterial as a material for the functional layer and a solvent dissolvingthe functional material, and filling an inkjet device having an inkejection nozzle with the ink, the functional material having aweight-average molecular weight greater than zero and equal to or lessthan 100,000; preparing a substrate on which the functional layer is tobe formed; positioning the inkjet device above the substrate, andcausing the inkjet device to eject a drop of the ink onto the substrate;and forming the functional layer by drying the ink ejected onto thesubstrate; and, wherein in the preparation of the ink, when a value Zdenotes a reciprocal of the Ohnesorge number Oh determined by density ρ(g/m³), surface tension γ (mN·m), and viscosity η (mPa·s) of the ink anda diameter r (mm) of the ink ejection nozzle, the value Z is within arange of Formula 1, in the ejection of the drop of the ink, speed V(m/s) of the ejected drop of the ink is within a range of Formula 2, andthe value Z and the speed V (m/s) satisfy Formula 3:0.7≦Z≦13where Z=1/Ohnesorge number Oh=(r·ρ·γ)^(1/2)/η  (Formula 1);3≦V≦6  (Formula 2); andV≦−2.17 Ln(Z)+8.47  (Formula 3).
 9. The method of forming the functionallayer of claim 8, wherein the value Z is two or more and is ten or less,and the speed V is 3 m/s or more and is 5 m/s or less.
 10. The method offorming the functional layer of claim 8, wherein the density ρ of theink is more than 827 g/m³ and is 1190 g/m³ or less, the surface tensionγ of the ink is more than 27.3 mN·m and is 41.9 mN·m or less, theviscosity η of the ink is more than 2.4 mPa·s and is 35.0 mPa·s or less,and the diameter r of the ink ejection nozzle is 0.02 mm or more and is0.03 mm or less.
 11. An ink that is ejected onto a substrate by aninkjet device having an ink ejection nozzle, and is dried to form afunctional layer, comprising: functional material as a material for thefunctional layer, the functional material having a weight-averagemolecular weight greater than zero and equal to or less than 100,000;and a solvent dissolving the functional material, wherein when a value Zdenotes a reciprocal of the Ohnesorge number Oh determined by density ρ(g/m³), surface tension γ (mN·m), and viscosity η (mPa·s) of the ink anda diameter r (mm) of the ink ejection nozzle, the value Z is within arange of Formula 1, speed V (m/s) at which the ink is ejected is withina range of Formula 2, and the value Z and the speed V (m/s) satisfyFormula 3:0.7≦Z≦13where Z=1/Ohnesorge number Oh=(r·ρ·γ)^(1/2)/η  (Formula 1);3≦V≦6  (Formula 2); andV≦−2.17 Ln(Z)+8.47  (Formula 3).
 12. The ink of claim 11, including thesolvent and the functional material as a material for the functionallayer of an organic light-emitting element; and being ejected onto abase layer of the substrate for the organic light-emitting element anddried to form the functional layer between a first electrode included inthe base layer and a second electrode opposing the base layer.
 13. Theink of claim 11, wherein when the speed V is 3 m/s or more and is 5 m/sor less, the value Z, which is determined by the density ρ (g/m³), thesurface tension γ (mN·m), and the viscosity η (mPa·s) of the ink, is twoor more and is ten or less.
 14. The ink of claim 11, wherein when thediameter r of the ink ejection nozzle is 0.02 mm or more and is 0.03 mmor less the density ρ of the ink is more than 827 g/m³ and is 1190 g/m³or less, the surface tension γ of the ink is more than 27.3 mN·m and is41.9 mN·m or less, and the viscosity η of the ink is more than 2.4 mPa·sand is 35.0 mPa·s or less.
 15. A substrate having the functional layermanufactured by using the ink of claim
 11. 16. The organiclight-emitting element having the functional layer manufactured by usingthe ink of claim
 12. 17. An organic display panel including the organiclight-emitting element having the functional layer manufactured by usingthe ink of claim
 12. 18. An organic light-emitting device including theorganic light-emitting element having the functional layer manufacturedby using the ink of claim
 12. 19. An organic display device includingthe organic light-emitting element having the functional layermanufactured by using the ink of claim
 12. 20. An inkjet device that isfor containing therein ink including functional material as a materialfor a functional layer and a solvent dissolving the functional material,and ejects the ink from an ink ejection nozzle onto a substrate to formthe functional layer, the functional material having a weight-averagemolecular weight greater than zero and equal to or less than 100,000,wherein when a value Z denotes a reciprocal of the Ohnesorge number Ohdetermined by density ρ (g/m³), surface tension γ (mN·m), and viscosityη (mPa·s) of the ink and a diameter r (mm) of the ink ejection nozzle,the value Z is within a range of Formula 1, speed V (m/s) at which theink is ejected is within a range of Formula 2, and the value Z and thespeed V (m/s) satisfy Formula 3:0.7≦Z≦13where Z=1/Ohnesorge number Oh=(r·ρ·γ)^(1/2)/η  (Formula 1);3≦V≦6  (Formula 2); andV≦−2.17 Ln(Z)+8.47  (Formula 3).
 21. The inkjet device of claim 20,wherein the functional material included in the ink is a material forthe functional layer of an organic light-emitting element, and the inkis ejected onto a base layer of the substrate for the organiclight-emitting element to form the functional layer between a firstelectrode included in the base layer and a second electrode opposing thebase layer.
 22. A substrate having the functional layer manufactured byusing the inkjet device of claim
 20. 23. The organic light-emittingelement having the functional layer manufactured by using the inkjetdevice of claim
 21. 24. An organic display panel including the organiclight-emitting element having the functional layer manufactured by usingthe inkjet device of claim
 21. 25. An organic light-emitting deviceincluding the organic light-emitting element having the functional layermanufactured by using the inkjet device of claim
 21. 26. An organicdisplay device including the organic light-emitting element having thefunctional layer manufactured by using the inkjet device of claim 21.